House hunters: the climate change edition

As part of my job, I’m required to go to conferences on climate change and education. This is always fun—who doesn’t love breaking away from the office?—but also sometimes rather shocking. I actually choked on my coffee at a recent talk when a presenter declared that Massachusetts was the most energy efficient state in the union. If Massachusetts is the leader of the pack, I feel sorry for the rest of the country.

As an academic and long-time resident of the Boston area, I saw fancy new university buildings constructed with limited appreciation for the local climate—think open and airy 4-story high ceilings, with automatic doors facing prevailing ocean winds, or “green” residential halls where students had to open the windows in the winter to let the heat out as the thermostat, it turned out, was mostly for show. As a renter, I never once lived in a unit with double-pained windows or insulation: unsexy, yes, but fundamentals of energy efficiency in the frosty winters.

Efficiency, though, is the least of issues for Boston tenants. I had landlords who had to be threatened to replace broken refrigerators and busted locks. When my then-boyfriend’s ceiling caved in over his bed due to a leaky roof, his landlord simply patched the ceiling with plaster, which lasted about 3 days, before it rained again. Moving out west was a lesson in luxury – in California, your landlord will actually change your light bulbs if you ask him. The thought of this is so mind-boggling to me that I have never actually requested it. I hardly believe it.

So, as a nomadic academic type, there is nothing I understand better than the importance of finding good housing. Energy efficiency, maintenance and repairs, safety, comfort, these are all the things people look for. And really, we are not alone. Most animals feel the same way.

Never is this more apparent than with animals who shop for their own mobile homes. You already no doubt have heard about hermit crabs and how they take over other (dead) animal’s shells over their lifetime, upgrading to new homes as they grow for a “better fit”. There has been all sorts of research dating back over 30 years in what makes a good shell for hermit crabs, and man, are they picky. They have a preference for weight, size, center of gravity and even the species of animal the shell came from (1).

How do the hermit crabs make their decisions? They have a “sniffing” behavior, where they use their antennule (small antenna) to check out possible shells. If it’s a step up, they move on to their new digs, even if that shell is otherwise occupied. This sniffing behavior is important to hermit crab success. It’s their way of gathering sensory info to make their decision to move. To hermit crabs, it’s all about the sniff.

As you know from my previous blogs, though, climate change has the potential to change the behaviors of many sea animals, and hermit crabs are no different. With increased carbon dioxide in the atmosphere, there will be increased carbon dioxide in the ocean, which leads to a change in ocean water pH. This change in pH is the thing that could mess with the hermit crab’s ability to assess their new shell.

When exposed to a more acidic environment (lower pH), hermit crabs “sniffed” potential shells less and were less likely to switch to better shells in the end. Basically the change in sea water pH disrupted their ability to assess their potential new homes (2). Call the broker!

Of course, this inability to assess living spaces is far worse for the hermit crab than it is for your average renter in Boston. If you choose a place with a leaky ceiling in Boston, you can at least stay over your girlfriend’s house – who fortunately for you, lives on the ground floor. If you choose poorly as a hermit crab, you expose yourself to greater predation, or a heavier shell, or one that can’t accommodate your fat butt – it’s just not a good thing. As a hermit crab, your home is all you’ve got – and with climate change, hermit crabs might need to find themselves a girlfriend’s couch to sleep on too.

Further Reading:
(1) The importance of various shell characteristics to the shell-selection behavior of hermit crabs
(2) Reduced sea water pH disrupts resource assessment and decision making in the hermit crab Pagurus bernhardus

Minda Berbeco has a PhD in Biology from Tufts University and is a science writer in the Bay area. She was surprised to learn when researching this article that hermit crabs chirp when angry. Yes, chirp. Freaky.

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